The invention relates to a seal for a machine part axially displaceable through an annular, internally-open groove in a stationary machine part.
Seals of this type are usually called U rings. They serve to seal reciprocating piston rods or pistons against a liquid under pressure. In high-pressure applications, it is customary to use several U rings in a row. With the usual designs, where the spacing of the dynamically-acting sealing lip from the associated end face of the groove accommodating the seal is bigger than or the same as that of the statically-acting sealing lip, this may result in a buildup of pressure in the space between the individual U rings which, in turn, may result in their premature failure.